Standardized applications of electroluminescence imaging for efficient investigation of potential-induced degradation shunting in crystalline silicon photovoltaic module

Abstract

Potential-induced degradation shunting (PID-s) detrimentally impacts a photovoltaic (PV) module’s performance and lifetime. Hence, early PID-s investigation in a field and precise laboratory testing of module PID-s susceptibility is essential before field deployment. Electroluminescence (EL) imaging has been widely used for PID-s investigation, but a lack of standardization exists in its application, which leads to inefficient PID-s investigation. In this work, standardized EL methods are developed to efficiently investigate PID-s. From the perspective of laboratory and field applications, three general cases are considered as per the availability of reference. Critical aspects of EL imaging and PID-s such as EL current, PID-s nature, and severity are analyzed using two diode model of a PV cell. Based on this analysis, an EL method is optimally developed for each case, including the selection of magnitude and number of EL current, PID-s index to represent the PID-s, and EL threshold equivalent to PID-s qualification criterion (5 % STC power loss (Ploss)) used in IEC TS 62804-1. Proposed methods were experimentally validated on PID-s modules, and cell level PID-s investigation performance is compared with the standard I-Vmeasurements. Results show that the EL methods efficiently investigate PID-s before significantPlossresults (≤5%). For the quantitative PID-s investigation, empirical correlations have been derived relating normalized cellPlossas the sole function of PID-s index, which estimatesPlosswith ±3 % relative error. Thus, the proposed work optimally utilizes the potential of EL imaging and enables effective qualitative as well as quantitative PID-s investigation.